However, officials privately acknowledged that the plans could be delayed by legal challenges over whether they discriminate against some drink producers.

“It could take more than a year,” one Department of Health source said.

Gavin Partington, of the Wine and Spirits Association, said producers were “considering their options” over legal action.

“Minimum unit pricing is a blunt tool which would both fail to address the problem of alcohol misuse and punish the vast majority of responsible consumers,” he said.

“As government ministers acknowledge, it is also probably illegal.”

The European Commission sounded a warning to Britain about the policy, saying it believed “minimum tax rates to be preferable to minimum pricing for alcohol”.

“Minimum tax rates put all products on an equal footing from a market perspective, whereas minimum prices can increase the profit margin of products with the lowest production cost,” a spokesman said.

This could mean the policy falls foul of European trade rules dictating there should be “no discrimination between imported goods and domestic goods”.

A Downing Street spokesman said: “It’s easy to say it’s probably illegal but it’s never been done and there’s no test case so far. Scotland has had fairly positive conversations with Europe about it.”

He said that the Government would make sure any final decisions that came out of the consultation were legal before they were introduced.

* David Cameron has been accused of using his Home Secretary as a “human shield” to deflect bad Budget headlines in only the fourth Friday statement to MPs in a decade.

Theresa May announced a minimum price for alcohol in Parliament, while the previous three statements all related to national emergencies: the Iraq War, Libya and swine flu.

Yvette Cooper, the shadow home secretary, said it was a weak attempt to distract from negative reactions to the Budget.

Amid angry scenes in the House of Commons, Yvette Cooper told the half-empty chamber that Government statements were rarely made to MPs on a Friday - a day normally reserved for backbench business – unless they were related to national emergencies.

The shadow home secretary was reportedly forced abandon a constituency trip as she boarded a train at Kings Cross St Pancras station after being given two hours notice that the announcement would occur at 11am.